Dynamometer and related assessment method

ABSTRACT

Dynamometer ( 1 ) and related method for assessing the force ( 1 ) exerted at hand level, said dynamometer comprising a fixed frame ( 2 ), a pair of levers ( 3,4 ) apt to be taken hold of by a user, at least one lever being movable, a contrast element having a known resistance parameter, connected to the movable lever in order to contrast the displacement thereof, and displacement measuring means ( 10 ), associated to the movable lever in order to measure the displacement θ thereof.

The present invention refers to a dynamometer for assessing the forceexerted at hand level and to a related assessment method.

As it is known to those skilled in the art, kinesiology is thediscipline that, combining notions of anatomy, physiology and mechanics,studies human and animal motion, with specific regard to the muscularcontraction mechanisms underlying said motion. A specific branch ofkinesiology studies hands. In that specific field, a type of clinicaltest often used for diagnostic purposes is the assessing of the muscularcontraction force of hands and/or of individual fingers, and inparticular the detecting of the force levels and the possible variationsthereof in one or more sample muscles, optionally in response to varioustypes of stimulus or stress.

Notwithstanding the remarkable importance of this type of tests in thehighlighting of eventual functional problems in patients, to date noadequate technical means is available for the carrying out thereof.

In fact, said tests are mostly carried out manually by health workers,in particular by physician or physiotherapist operators, requiringremarkable care, skill and sensitivity thereby. However, even in thepresence of these capabilities, the test results are anyhow related tothe operator's subjective perception, and as such often they arerepeatable neither by different operators, nor by the same operator.Moreover, a test thus carried out is scarcely sensitive to minimal forcevariations which might instead yield useful diagnostic indications.

In light of the above, this type of test is not accepted by thescientific and academic community.

Moreover, assessment methods of the force exertable by human body areknown, which employ a weight of known entity connected to a displacementsystem of the rope-and-pulley type, said weight being lifted by thepatient with a rope-applied handgrip. Other methods instead obtain themuscular force by measuring the flexion of semirigid levers caused bythe patient's action.

However, the technical means employed in these latter methods merelyprovide approximate and low-sensitivity force measurements, moreoverbeing rather awkward to use.

The technical problem underlying the present invention is to provide adynamometer and a related assessment method of the muscular workovercoming the drawbacks abovementioned with reference to the known art.

This problem is solved by a dynamometer for assessing the force exertedat hand level according to claim 1.

According to the same inventive concept, the present invention furtherrefers to a method for measuring the force exerted at hand levelaccording to claim 18. The present invention provides several relevantadvantages. The main advantage lies in that it provides an instrument ofappreciable sensitivity apt to assess the force exerted at hand level ina repeatable, simple and reliable manner.

Other advantages, features and modes of employ of the present inventionwill be made apparent from the following detailed description of someembodiments thereof, given by way of a non-limiting example. Referencewill be made to the figures of the attached drawings, wherein:

FIG. 1 is a perspective view of an embodiment of the dynamometeraccording to the present invention;

FIG. 2 is a partially sectional perspective view of the dynamometer ofFIG. 1;

FIG. 3 is a block diagram of the dynamometer of FIG. 1; and

FIG. 4 is a partially sectional perspective view of the dynamometer ofFIG. 1 during operation.

With initial reference to FIG. 1, a dynamometer for assessing the forceexerted at hand level is generally indicated with 1. As it will beapparent from the following description, the dynamometer 1 is apt toassess the force exerted by a hand in its entirety as well as by itsindividual fingers.

The dynamometer 1 comprises a fixed frame, in form of a substantiallyparallelepiped-shaped outer casing 2.

With reference now also to FIG. 2, to the frame 2 there are connected afirst and a second lever, 3 and 4, respectively. In particular, thefirst lever 3 is made fixed to the frame 2 by conventional fasteningmeans. The second lever 4 is instead movable with respect to the frame2, and therefore with respect to the first lever 3, being rotatablyconnected to the frame by means of a shaft 5 fixed to the lever 4itself.

Said connection of the levers 3 and 4 to the frame 2 is carried out atrespective end portions of the levers themselves. Moreover, these leversproject for a prevalent portion of their length outside of the frame 2,at a front slot 6 of elongated shape thereof.

Each lever 3, 4 bears, at said projecting portion, a handgrip profile,and in particular three bays 7, each apt to receive one finger.

Always with reference to FIG. 2, the movable lever 4 is furtherconnected, at an intermediate portion thereof located internally to theframe 2, to a contrast element 8 apt to oppose a predeterminedresistance to the motion of the lever 4. In particular, in the presentembodiment this contrast element consists of a helical extension springhaving known rigidity. This spring bears, at its ends, suitable hookingportions for connection to the movable lever 4 and to the frame 2,respectively. In particular, the connection of the spring 8 to thelatter is carried out at an inner ledge 9 of the frame 2.

In a quiescent condition, i.e. in the absence of forces applied to themovable lever 4, the spring 8 lies in a condition of absence of tension,and it holds the former at a position angularly spaced from the fixedlever 3.

The dynamometer 1 further comprises an angular potentiometer 10 fastenedto the frame 2, said shaft 5 being a part thereof. The potentiometer 10is apt to measure the angular displacements of the movable lever 4following a force exerted by the user against the elastic return forceof the spring 8.

The potentiometer 10 is of a known marketed type, hence a furtherdescription thereof will be omitted.

In particular, a type marketed potentiometer suitable for implementingthe dynamometer 1 is the “MEGGITT CITEC” one, having the followingspecifications: resistor element: CERMET; power rating; 2 W at 70°;maximum operating voltage: 315 W; resistance tolerance: +/−10%; thermalcoefficient: +/−150 ppm/° C; final resistance: 3 W max; rotation rating:210° electrical, 270° electrical, 270° mechanical; rotational durationoperations: 25,000; operating temperature range: −55° C. to +125° C.;body dimensions; diameter 21 mm, length 12.7 mm; shaft: diameter 6.35mm, length 25 mm (metal); mounting bush: diameter 9.35 mm, length 10 mm(metal).

As it is shown in FIG. 3, in the present embodiment the dynamometer ofthe invention also comprises hardware and software measurementprocessing means, in particular a PC processor 11 connected to thepotentiometer 10 by conventional type data reception/transmission lines.In particular, the processor 11 is apt to compute the force exerted bythe user according to the rigidity value of the helical spring 8 and tothe displacement measurement provided by the potentiometer 10, as wellas further derivative quantities, like e.g. the work performed by saidforce.

It will be understood that, from said data, the computing of the forceexerted by the user against the elastic return force 8 can be carriedout by means of mere trigonometric algorithms, adopting the knownformulas for assessing the motive power applied to a lever, in this casethe force exerted by the user, knowing the resisting force, in this casethe elastic return force of the spring 8, and the related lever arms andconsidering that the fulcrum of the lever 4 is located at one endthereof, in correspondence of the axis of the shaft 5.

In particular, with reference to FIG. 4, indicating by L the (set)distance interposed between the hooking spot of the spring 8 to themovable lever 4 and the center of the pin 5, and by θ the angulardisplacement of the lever 4 itself caused by the action force exerted bythe user thereon and measured by the potentiometer 10, the correspondingextension A of the spring 8 can be approximated as arc subtended by theangle θ, i.e.:A≅Lθ,

Alternatively, the extension A can be approximated as chord subtendedalways by the angle θ, i.e.:A≅2L sin(θ/2),

Both such approximations are wholly acceptable within the context of thetype of assessment to be carried out, also in light of the small angulardisplacements involved. Moreover, always by virtue of such small entityof the involved displacements, the transversal deformation of the spring8 due to shear stresses is negligible.

Upon computing the extension A, the processing means 11 compute thereturn force F of the spring 8, according to the known relation:F=k A,where k indicates the (known) rigidity of the spring 8.

Then, the actual force exerted by the user can be estimated consideringalso the distance of the handgrip point from the fulcrum of the lever 4,a distance that varies according to the type of test carried out.Apparently, handgrip type being equal, also the resisting force F can beconsidered as an estimate of the motive power force actually exerted bythe user.

Moreover, clinically an entity F′ is often employed, having thedimensions of a work or energy, yet in turn indicated as force andassessed in (kg_(r)m), and that, e.g. for the force F, can be computedas:F′=F A.

Hence, also this quantity could be computed by the means 11.

Moreover, the processing means 11 are connected, always by conventionaltype data transmission lines, to means 12 for displaying the result ofthe measuring, that in the present embodiment is a monitor apt tographically display the results.

The hereto-described processing and displaying means are well-known tothose skilled in the art, being widely used to carry out biomechanicallaboratory measuring for human motion analysis, hence a furtherdescription thereof will be omitted. In particular, these means providea vast variety of processing and presenting options of the measurements,executable with known type hardware and software tools. Moreover, theformer will typically have a user interface, comprising e.g. a keyboard,in order to enable the operator to input data related to the type oftest carried out, and optionally to store the results thereof.

The dynamometer 1 further comprises a known type analog/digitalconverter interposed between the potentiometer 10 and the processingmeans 11, as well as conventional type power supply means 13, e.g. anaccumulator connectible both to the potentiometer 10 and to theprocessor 11, optionally associated to a known type transformer. Suchprocessing means enable also to carry out electronic calibration steps.

Of course, the dynamometer of the invention can also be power-supplieddirectly from the mains of the premises hosting it.

As it is shown in FIG. 1, at a sidewall of the frame 2 the dynamometer 1further comprises an ON/OFF push-button 14, a connecting terminal 15 forconnecting to the processor 11 and a terminal 16 for connecting to theaccumulator 13. As also these elements and the associated components areof conventional type, a further description thereof will be omitted.

The operation of the dynamometer of the invention will hereinafter bemade apparent. In particular, in order to carry out a kinesiologicaltest for measuring the muscular contraction force at hand level, anoperator, upon pre-arranging the dynamometer 1, will have the user graspthe two levers 3 and 4 of the dynamometer 1 with the fingers of thehand, left or right, to be involved in the measuring. H.g., a type oftest provides the assessment of the force associated to the thumb andforefinger flexors. Therefore, in this test each one of these twofingers engages a bay 7 of a respective lever 3 or 4.

Then, the user exerts a force onto the two levers, and, acting againstthe return force of the spring 8, determines the longitudinaldeformation thereof, and hence the angular displacement of the movablelever 4. This displacement is sensed and measured by the potentiometer10, which transmits the related data to the processing unit 11, whereatthe value of the force exerted is computed as above illustrated.

The quantities measured and those computed thereby are then graphicallyor numerically displayed onto the monitor 12, optionally also in termsof a time profile. It will be appreciated that the dynamometer of theinvention is quite flexible with respect to the option of assessingdifferent entities associated to the force exerted by the user. Inparticular, those skilled in the art will appreciate that, besides theestimate of quantities such as the abovementioned force and work, fromthe force measuring carried out ‘from the outside’ like theabovedescribed ones there can be estimated, by known empiricalrelations, the ‘inside’ muscular contraction force.

Moreover, the dynamometer of the invention enables accurate andremarkably sensitive measuring. In particular, with the abovementionedcomponents there can be measured quantities F′ having a minimum value ofabout 2 kg_(r) m and a maximum value of about 14 kg_(r) m, with aresolution of about 200 g_(r) m.

It will further be appreciated that the dynamometer of the invention hasreduced dimensions and is extremely easy to employ, for the user as wellas for the operator. It will also be understood that the peculiar 3-baystructure of the lever handgrip enables the carrying out of a remarkablywide variety of tests, enabling different modes of handgrip.

It will be understood that the present invention is suitable for severalembodiments alternative to the hereto-described one, some of which willbriefly be illustrated hereinafter with reference to the sole aspectsdifferentiating it from the hereto-considered first embodiment.

First of all, the dynamometer of the invention could have displacementmeasuring means alternative to the abovedescribed angular potentiometer.Of course, the type of these means depends also on the type ofmovability of the movable lever of the invention. The latter could,e.g., have a translational degree of freedom in alternative to or inassociation with the rotational one of the abovedisclosed embodiment.Moreover, the displacement measuring means could be directly connectedto the elastic element rather than to the movable lever.

Furthermore, the dynamometer, and in particular the processing meansthereof, could be preset to enable opposite-sense force measuring E.g.,with reference to the abovedescribed embodiment, there could be provideda deformation both in extension and in compression of the elasticelement.

The abovedescribed elastic element could further have a pre-tensioningstate, i.e. a pre-loading state, also in the quiescent conditionthereof. Moreover, a further embodiment provides the presence of aplurality of elastic elements arranged in series or in parallel, so asto increase the measuring range of the dynamometer.

Moreover, the dynamometer can comprise a contrast element different fromthe abovedescribed elastic element, like e.g. a hydraulic element.Therefore, the latter would have a known resistance parameter differentfrom the rigidity of the elastic element itself.

Furthermore, the dynamometer levers could have a handgrip different fromthe abovedescribed one, apt to satisfy specific testing needs. Inparticular, in order to allow an optimum carrying out of the tests morefrequently adopted in kinesiology, the movable lever could have a bayspecifically shaped to receive a forefinger and optionally a further bayapt to receive a middle finger, and the fixed lever a bay specificallyshaped to received a thumb.

According to a further simplified embodiment, the dynamometer of theinvention can provide the measurement processing means to be directlyincorporated into the frame receiving the levers introduced withreference to the abovedisclosed first embodiment. In this case, saidmeans can also consist of a microprocessor, connected to thedisplacement measuring means by interposition of an analog/digitalconverter, it also directly received with the frame. Moreover, in thisembodiment the means for displaying the result of the measuring couldconsist, instead of a monitor, of a simpler digital display apt toindicate to the operator the force level reached. Said digital displaycan be fixed with the frame or located thereabout. Moreover, in thiscase as well the dynamometer can enable an electronic calibration andallow resetting steps by operation of a suitable push-button.

In this latter embodiment the dynamometer of the invention is extremelyeasy to carry, thereby enabling to easily carry out ‘on the field’ forcemeasuring i.e., not necessarily on clinical premises.

Moreover, the dynamometer of the invention can have selecting means,e.g. one or more push-buttons, located directly onto the casing or framereceiving the levers and apt to allow starting a measuring sessionand/or selecting the type of measuring to be carried out.

Furthermore, the levers of the dynamometer can also be both movable.

According to a further embodiment, the contrast element can have aselectivity variable resistance, and in particular an adjustable one,thereby enabling the measuring of different force ranges, i.e. thecarrying out of a wider range of exercises. This adjusting of theresistance opposed to the motion of the movable lever is attainable,e.g., associating to the contrast element, for instance to theaboveintroduced helical spring, an actuator apt to modify thepre-loading level thereof. This actuator in turn can be controlled, withknown modes and means, by the same user by operating suitable selectingmeans, e.g, a set of push-buttons each one corresponding to a respectiveresistance level. In the case of the helical spring, the actuator canconsist of an electromagnetic motor and related transmission means.Moreover, the preset resistance level can also be displayed onto asuitable display. By now, it will be apparent that the present inventionprovides also an assessment method for assessing the force exerted athand level, comprising the steps of:

-   -   having a user grasp, with one hand, a pair of levers as        hereto-described with reference to the dynamometer of the        invention;    -   having the user exert a force against the resisting action of        said contrast element;    -   measuring the displacement given by the user to the movable        lever; and    -   computing the force exerted according to the already described        modes.

The present invention was hereto described with reference to specificembodiments thereof. It is understood that there may be otherembodiments afferent to the same inventive kernel, all falling withinthe protective scope of the appended claims.

1. A dynamometer (1) for assessing the force (F) exerted at hand level,comprising: a fixed frame (2); a pair of levers (3, 4) apt to be graspedby a user, at least one (4) of which is movable with respect to saidframe; a contrast element (8) having a known resistance parameter (k),connected to said at least one movable lever to contrast a displacement(θ) thereof; displacement measuring means (10), associated to said atleast one movable lever to measure the displacement (θ) thereoffollowing operation by the user; and means (11) for processing themeasuring carried out.
 2. The dynamometer (1) according to claim 1,wherein at least one lever (3, 4) of said pair has an anatomicalhandgrip (7).
 3. The dynamometer (1) according to claim 2, wherein saidanatomical handgrip comprises three bays (7), each apt to receive afinger.
 4. The dynamometer (1) according to claim 2, wherein a firstlever (4) of said pair has a bay (7) specifically shaped to receive aforefinger and second lever (3) of said pair has a bay (7) specificallyshaped to receive a thumb.
 5. The dynamometer (1) according to claim 4,wherein said first lever (4) is movable with respect to said frame (2)and said second lever (3) is fixed with said frame.
 6. The dynamometer(1) according to claim 4, wherein said first lever (4) has a further bay(7) specifically shaped to receive a middle finger.
 7. The dynamometer(1) according claim 1, wherein said contrast element comprises anelastic element (8) having known rigidity.
 8. The dynamometer (1)according to claim 7, wherein said elastic element comprises a helicalextension spring (8).
 9. The dynamometer (1) according to claim 1,wherein said contrast element (8) has an adjustable resistance.
 10. Thedynamometer (1) according to claim 9, wherein said contrast elementcomprises an elastic element (8) having known rigidity and saiddynamometer comprises an actuator apt to modify the preloading levelof-said contrast element (8).
 11. The dynamometer (1) according to claim9, further comprising selection means operable by a user to select theresistance level of said contrast element (8).
 12. The dynamometer (1)according to claim 9, further comprising display means apt to indicatethe resistance level of said contrast element (8).
 13. The dynamometer(1) according to claim 1, wherein said at least one movable lever (4) isrotatably connected to said frame (2).
 14. The dynamometer (1) accordingto claim 13, wherein said displacement measuring means comprises anangular potentiometer (10) located at said rotatable connection betweenthe movable lever (4) and the frame (2).
 15. The dynamometer (1)according to claim 1, wherein said processing means (11) of themeasuring carried out is apt to output an entity (F′) having thephysical dimensions of work.
 16. The dynamometer (1) according to claim1, further comprising means (12) for graphically displaying themeasuring carried out.
 17. A method for measuring a force (F) exerted athand level, comprising the steps of: having a user grasp, with one hand,a pair of levers (3, 4) located on a frame (2), at least one (4) thereofbeing movable; having the user exert the force (F) against a resistingaction of a contrast element (8) connected to the at least one movablelever and having a known resistance parameter (k); measuring adisplacement (θ) given by the user to the at least one movable lever;and processing the measuring carried out in such a way to compute theforce (F) exerted according to the measured displacement and to theresistance parameter of the contrast element.
 18. The method accordingto claim 17, wherein said step of having a user grasp a pair of levers(3, 4) provides that the thumb and the forefinger of a user's hand eachgrasp a respective lever of the pair of levers, thereby enabling theassessment of the force of the flexors of such fingers.
 19. The methodaccording to claim 17, wherein said step of having a user grasp a pairof levers (3, 4) provides that the thumb grasp the fixed lever (3) andthat the forefinger and the middle finger grasp the movable lever (4).20. The method according to claim 17, wherein said resisting action isan elastic return force.
 21. The method according to claim 17, whereinsaid step of measuring the displacement given by the user to the atleast one movable lever (4) provides the measuring of an angulardisplacement (θ) of said lever.
 22. The method according to claim 17,comprising the further step of computing the work (F′) performed by theuser upon exerting the force (F) to be measured.